venti modes.pptx

MODES AND PRINCIPLES MECHANICAL VENTILATION

1. VARIOUS MODES OF MECHANICAL VENTILATION

2. GOALS SAFETY – no VILI /CILI – acute phase COMFORT – low sedation, good synchrony - stablisation phase LIBERATION – early weaning – stablisation and recovery phase of disease

3. COMPONENTS OF BREATH Start (inspiration) = TRIGGER Maintain /fixed = LIMIT End of inspiration =CYCLE Expiration A B C

4. TRIGGER VARIABLES Machine = time :- based on the set time interval Pt – pressure / flow / neural Pressure - patient assisted :- based on the drop in airway pressure Flow - patient assisted :- flow triggering strategy uses a combination of continuous flow and demand flow Neural – newer modes (NAVA )

5. LIMIT VARIABLES If one of variables (pressure, volume or flow) is not allowed to rise above a preset value during inspiratory time, it is termed a limit variable. The breath delivery continues, but the variable is held at the fixed preset value. TYPES- Pressure limit Flow limit Volume limit

6. CYCLE VARIABLES A measurement that causes the end of inspiration. This variable must be measured by the ventilator and used as feedback signal to end inspiration and then allow exhalation to begin. It can be:- Pressure-cycled Volume-cycled Flow-cycled Time-cycled

7. BASICS SHAPES OF WAVEFORM Square Ramp Sine wave

8. SCALARS Plotted against time( x axis) Press-time Flow-time Volm-time

9. LOOPS Plotted against volume Press- volm Flow- volm

10. CONTROLLED MANDATORY VENTILATION (CMV) Also known as continuous mandatory or control mode. The ventilator delivers the preset tidal volume or pressure at a set time interval (time-triggered frequency). Indications: Initial stages of mechanical ventilation when patient fights the ventilator. DISADVANTAGES – NEED FOR EXESSIVE NMBs – cinm , muscle atrophy

11. CHARACTERISTIC OF CONTROL MODE

12. ASSIST/CONTROL(AC) In assist/control(AC) mode the patient may increase the frequency(assist) in addition to the preset mechanical frequency(control). Each assist breath provides the preset mechanical tidal volume .

13. Indications: Used to provide full ventilatory support for patients when they are first placed on mechanical ventilation. Typically used for patients who have a stable respiratory drive( stable spontaneous frequency of at least 10 to 12/min)& therefore trigger ventilator into inspiration. Requirement : synchrony

14. VOLUME CONTROL MODE Set volm is delivered with each breath Volm delivery fixed, pressure will very, depending upon pulmonary compliance and airway resistance TRIGGER – time LIMIT – flow CYCLE - volume

15. Advantage – can regulate tidal volm and minute ventilation Disadvantage – 1) Variable PIP based on lung mechanics- Barotrauma

16. 2) Related to flow and sensitivity setting which may lead to pt venti asynchrony. Constant flow may not match pt demand.

17. PRESSURE TIME SCALAR IN VOLUME CONTROL

18. PRESS CONTROL Allows clinicians to set a maximum pressure level Using this mode would reduce the peak inspiratory pressure while still maintaining adequate oxygenation(PaO2) and ventilation(PaCO2) therefore reducing the risk of barotrauma in such patients. The pressure controlled breaths are time trigggered by a preset respiratory rate. Once inspiration begins, a pressure plateau is created and maintained for a preset inspiratory time. Pressure controlled breaths are therefore time triggered, pressure limited and time cycled.

19. Decelerating flow pattern More comfortable for spontaneously breathing pts Disadvantage: Volm delivery varies

20. PRESSURE SUPPORT VENTILATION (PSV) PSV is used to lower the work of spontaneous breathing and augment the spontaneous tidal volume. PSV applies a preset pressure plateau to the patient’s airway for the duration of spontaneous breathing. TRIGGER - pt LIMIT – pressure CYCLE – flow (breath cycles when flow reaches some proportion of peak flow say 25%)

21. Dual Control Breath-to-Breath pressure-limited time-cycled ventilation Pressure Regulated Volume Control Servo 300 Maquet Servo- i

22. PRESSURE REGULATED VOLUME CONTROL Closed loop system Matches pt.’s demand Ventilator measures VT delivered with VT set on the controls. If delivered VT is less or more, ventilator increases or decreases pressure delivered until set VT and delivered VT are equal

23. Delivers patient or timed triggered, pressure-regulated (volume controlled) and time-cycled breaths

24. PRESSURE REGULATED VOLUME CONTROL The ventilator will not allow delivered pressure to rise higher than 5 cm H2O below set upper pressure limit Example: If upper pressure limit is set to 35 cm H2O and the ventilator requires more than 30 cm H2O to deliver a targeted VT of 500 mL, an alarm will sound alerting the clinician that too much pressure is being required to deliver set volume (may be due to bronchospasm, secretions, changes in CL, etc.)

25. PRVC Measure VT Compare to set VT Same inspiratory pressure  inspiratory pressure  inspiratory pressure Test breath Less Equal More

26. PRVC (Pressure Regulated Volume Control) PRVC. ( 1 ), Test breath (5 cm H 2 O); ( 2) pressure is increased to deliver set volume; ( 3) , maximum available pressure; ( 4) , breath delivered at preset E , at preset f, and during preset T I ; ( 5) , when V T corresponds to set value, pressure remains constant; ( 6) , if preset volume increases, pressure decreases; the ventilator continually monitors and adapts to the patient’s needs

27. PRVC (Pressure Regulated Volume Control) Disadvantages and Risks Varying mean airway pressure May cause or worsen auto-PEEP When patient demand is increased, pressure level may diminish when support is needed A sudden increase in respiratory rate and demand may result in a decrease in ventilator support

28. PRVC (Pressure Regulated Volume Control) Indications Patient who require the lowest possible pressure and a guaranteed consistent VT ALI/ARDS

29. PRVC (Pressure Regulated Volume Control) Advantages Maintains a minimum PIP Guaranteed V T Decreases WOB Allows patient control of respiratory rate Decelerating flow waveform for improved gas distribution Breath by breath analysis

30. Bi level mode of ventilation:- At either pressure level the patient can breathe spontaneously spontaneous breaths may be supported by PS P aw cmH 2 60 -20 1 2 3 4 5 6 7 Spontaneous Breaths Spontaneous Breaths

31. BiLevel Ventilation PEEP H PEEP L Pressure Support PEEP High + PS P aw cmH 2 60 -20 1 2 3 4 5 6 7

32. APRV (Airway Pressure Release Ventilation) Provides two levels of CPAP and allows spontaneous breathing at both levels when spontaneous effort is present Both pressure levels are time triggered and time cycled APRV always implies an inverse I:E ratio

33. APRV (Airway Pressure Release Ventilation) Allows spontaneously breathing patients to breathe at a high CPAP level, but drops briefly (approximately 1 second) and periodically to allow CPAP level for extra CO2 elimination (airway pressure release) Mandatory breaths occur when the pressure limit rises from the lower CPAP to the higher CPAP level

34. Airway Pressure Release Ventilation P aw cmH 2 60 -20 1 2 3 4 5 6 7 8 Spontaneous Breaths Releases

35. AIRWAY PRESSURE RELEASE VENTILATION:- Similar in concept to older forms of inverse ratio ventilation and bi level ventilation. Recruits more slowly filling alveoli and raises mean airway pressure without increasing tidal volume or applied PEEP. Unassisted spontaneous efforts during the inspiration enhances recruitment .

36. Inspiratory pressure set between 20 to 30 cmH20 Expiratory pressure set upto 2 to 3 cmH20 Inspiratory time: 3 to 5 seconds Expiratory time: 0.5 to 1 second I:E ratio between 4:1 and 10:1

37. APRV (Airway Pressure Release Ventilation) Indications Partial to full ventilatory support Patients with ALI/ARDS Patients with refractory hypoxemia due to collapsed alveoli Patients with massive atelectasis